It is already known to clean carpets by applying a liquid to the carpet which has detergent qualities and is capable of being beaten up into a foam by brushes or rollers which engage the carpet surface and drive foam, as it is formed, into the nap of the carpet or between fibers thereof so that the foam can lift soil to the surface from which the foam, liquid and entrained soil can be vacuumed away.
In the prior art devices of this type, the foam is formed or applied by means of a brush, a belt or a roll.
In practice it has been found that these earlier systems can be inefficient with respect to the cleaning effect because the foaming may be insufficient and the manner in which the foam is generated from the cleaning liquid may not permit sufficient quantities of air to be beaten into the liquid for most effective foam generation and application.